Automatic block signal system for railroads



Dec. 31, 1 935. R WHWEHORN 2,026,486-

AUTOMATIC BLOCK SIGNAL SYSTEM FOR RAILROADS Filed July 5, 1954 A Le I HI}- ug r g t Patented Dec. 31, 1935 PATENT OFFICE AUTOMATIC BLOCK SIGNAL SYSTEM FOR RAILROADS Arthur R. Whitehorn, Rochester, N. Y., assignor to General Railway Signal Company, Rochester, N. Y.

Application July 5, 1934, Serial No. 733,724

11 Claims. (01. 246-41) This invention relates to automatic block signal systems for single track railroads of the type commonly known as absolute-permissive-block systems.

In the usual absolute-pennissive-block or A. P. B. system, such as disclosed for example in the patent to S. N. Vfight No. 1,294,736, granted February 18, 1918, when a train enters the single track block between passing sidings and reverses its direction of movement, there may not be adequate signal protection; and one object of this invention'is to provide simple and effective means for controlling the intermediate signals in an A. P; B. system so as to afford proper and safe signallingprotection for such train movements.

Various characteristic features and advantages of the invention will be in part pointed out, and in part apparent, as the description progresses.

The accompanying drawing illustrates in a simplified and conventional manner some of the circuits for a typical absolute-permissive-block signal system, together with the circuits and controlling contacts constituting the improve ment of this invention.

The accompanying drawing shows only such relays and circuits as are particularly material to the present invention, the apparatus and circuitsfor a complete A. P'.B. system in one typical form having been shownancl described in detail in said Wight patent, to which reference may be made for additional information with respect to the structure and operation of the system as a whole.

In order to simplify the illustration and explanation, the invention has been illustrated in the accompanying drawing as applied to the control of two intermediate signals 6 and 8' governing east-bound traflic- (left to right) toward the end of. the passing siding PS, in a system of the type employing opposite pairs of intermediate signals; butv it should be understood that the same arrangement may be applied to the westbound intermediate signals 5 and T, and also to a system employing staggered intermediate signals.

The track is divided into track sections ST, ST, etc in the usual way, each having a track relay shown conventionally and designated 5TB, 6TH, etc. The signals are shown as the usual threeeposition motor operated semaphore signals, but color light signals, or any other suitable type of block signal may be employed. Each signal is controlled by a neutral-polar relay 511D, BHD etc., together with directional stick relays 5S, 1S, 8S, in the usual way; and each intermediate signal operates snap pole changers for governing the energization of the line circuit for the signal in the rear. The line circuit for relay 8HD for signal 8 is controlled by the usual pole changing contacts operated by the relay PC.

Considering the principles and mode of oper ation of the invention as applied to the approach signal 8, the circuit for the relay 8HD; which includes front contacts of the track relays 8TH, and 9TB in the usual way, has two multiple paths or branches connecting to the contacts of therelay PC, one path including a front contact l5 of the track relay IDTR, and. the other path including in multiple a back contact of the neutral armature it of the line relay 9HD, and a front contact oi the neutral armature in series with a contact of the polar .armature l1 closed when said relay SHD is energized with a polarity corresponding to clear or proceed.

Assume that a west-bound train leaves the passing siding PS and advances into a track section IT beyond the signals i and 8, .and further assume another following train has entered the track section IUT. In the ordinary A. P. B.

from the circuit of relay 8I-ID as it was in former A. P. B. systems, the first train in the track section 1T would. not have adequate signal protection. in attempting a reverse move back toward the siding.

The arrangement of circuits for controlling signal 8 in accordance with this invention prevents the signal 8 from indicating proceed under these conditions, because the presence of the train in track section IUT opens one branch. of the line circuit for relay 8HD at the front contact l5 of track relay HlTR, and the other branch of this line circuit is broken since relay 9HD is energized to give a caution indication. Consequently, signal 8 remains at stop for the first west-bound train under these conditions, thereby affording the necessary signal protection, and obviating the need for the train making its reverse move under flag protection, as ordinarily required under the operating rules.

It should be noted that the approach signal 8 is prevented from clearing for a reverse move only if there is a following train the track section HlT. This permits a train to make a reverse move under signal protection, if there is no other train present in position to accept the caution indication of the starting signal 9. In this connection, the branch circuit for energizing relay BHD including front contact I 5 of track relay IUTR, also includes a contact of a switch circuit controller, so that when the switch is opened to permit the train to come off of the siding, signal 8 will be put to stop.

The same principles may be applied to the control of the intermediate signal 6, with some variations in the arrangement of circuits. The line circuit for relay BHD includes two branches in multiple, one open if the relay l'HD is in condition to cause signal 1 to indicate caution, and the other branch open if signal 8 indicates caution or stop. Thus, if there is a following train in track section HIT, signal 6 cannot indicate proceed for a train in track section 5T, since both signals I and 8 indicate caution under these conditions and open both branches of the circuit for relay 61-11).

It will be noted that this invention involves electrical connections at the signal locations, and does not require any additional line wire or relays. The intermediate signals 6 and 8, controlled in a manner described, afford the desired detection for reverse movement, but do not interfere with a normal east-bound movement, line relays IHD and 9HD being deenergized in this case in accordance with the normal operation of an A. P. B. system to put all opposing signals to stop, so that signals 6 and. 8 may clear in the usual way.

Various adaptations and modifications of the specific arrangement of circuits shown and described may be made, without departing from the invention, particularly when the same principles and mode of operation are applied to control of color light signals; and it should be understood that the specific embodiment of the invention shown and described is merely illustrated.

What I claim is:-

1. In a railway signalling system of the character described, in combination with a starting signal controlled by a line relay, an approach signal, and a track section in the rear of the starting signal, and means controlled by said relay and a track circuit of said track section for preventing the approach signal indicating proceed for reverse train movements when said track section is occupied.

2. In a system of signalling of the character described, an approach signal governing traflic toward a siding, a starting signal governing traffic away from the siding, a track circuit in the rear of the starting signal, and means responsive to the presence of a train on said track circuit and the indication of said starting signal for preventing an indication of proceed of the approach signal for reverse train movements if said track section is occupied.

3. In a signalling system of the absolute-permissive-block type for single track railroads, the combination with a starting signal, an approach signal, a track circuit in the rear of the starting signal, and means for causing the approach signal to indicate'stop if said track circuit is occupied whenever the starting signal indicates caution.

4. In a system as described, a starting signal, an approach signal, a track circuit in the rear of the starting signal, a line circuit for controlling the approach signal including two branches in multiple, one of said branches including means for opening the same if a train is present on said track circuit, and the other branch including means for opening the same unless the starting signal indicates stop or proceed.

5. In a system of railway signalling of the 5 character described, the combination with a starting signal at a siding governing traflic away from the siding, an intermediate signal in a single track section for governing traflic toward the siding, and a line circuit for governing said in- 10 termediate signal including contacts associated with a relay controlling the starting signal and opened if the starting signal is controlled to indicate caution.

6. In a system of signalling of the character 15 described, a starting signal and an approach signal, a neutral polar relay for governing the starting signal, a line circuit for controlling the approach signal and including in multiple a back contact of the neutral armature of said relay and 20 a front contact in series with a polar contact closed only when'said relay is energized to cause said starting signal to indicate clear, and means for rendering said line circuit effective to control the approach signal when a track circuit in the 25 rear of the starting signal is occupied.

7. A block signal system for single track railroads of the type described characterized by the control of two intermediate signals governing traiiic toward a siding in accordance with the 30 presence of a train at the siding and the indications of a relay controlling the starting signal governing movement of such train from the siding, whereby signalling protection is afforded to trains making reverse movements. 35

8. In combination a single track section of railway track diverging into a double track portion through the medium of a track switch, wayside signals for governing trafiic in both directions through said single track section and including a 40 starting signal governing the movement of traffic into said single track section from said double track portion and an intermediate signal governing the movement of traffic toward said starting signal, electro-responsive means for each of said 45 signals which must be energized to cause its associated signal to indicate caution or clear, a. track circuit to the rear of said starting signal, and a control circuit for the electro-responsive means for said intermediate signal including 50 multiple branches one of which is open if said track circuit is occupied and the other of which is open if said starting signal is controlled to indicate caution, thereby causing said intermediate signal to indicate stop if there is a train 65 ready to accept said starting signal at caution.

9. In combination a single track section of railway track diverging into a double track portion through the medium of a track switch, wayside signals for governing traflic in both directions 60 through said single track section and including a starting signal governing the movement of traflic into said single track section from said double track portion and an intermediate signal governing the movement of trafiic toward said 5 starting signal, electro-responsive means for each of said signals which must be energized to cause its associated signal to indicate caution or clear,

a track circuit to the rear of said starting signal, and a control circuit for the electro-responsive 7 means for said intermediate signal including multiple branches one of which is open if said track switch assumes a reverse position and the other of which is open if said starting signal is controlled to indicate caution. I

10. In combination a single track section of railway track diverging into a double track portion through the medium of a track switch; wayside signals for governing traflic in both directions through said single track section and including a starting signal governing the movement of trafiic into said single track section from said double track portion and including a plurality of intermediate signals one to the rear of another and governing the movement of trafiic toward said starting signal; electro-responsive means associated with each signal which must be energized to cause its associated signal to indicate caution or clear; a track circuit to the rear of said starting signal; and a control circuit for the electro-responsive device of each of said intermediate signals including two multiple branches one of which is closed if the next opposing signal, comprising the starting signal or signal in advance thereof, is controlled to indicate caution and the other branch of which is closed if the track just to the rear of such opposing signal is 1 occupied.

11. In combination a single track section of railway track, wayside signals for governing trafiic in one direction through said section, wayside signals for governing traflic in the other direction through said section, electro-responsive means for each of said signals which must be energized to cause its associated signal to indicate caution or clear, and an energizing circuit for each of said electro-responsive devices including two branches in multiple one branch of which is open if there is a train between the next two opposing signals, and the other branch of which is open if the next opposing signal is controlled to assume the caution condition.

ARTHUR R. WHITEHORN. 

